Ghostly Neutrino Particles Provide a Peek into the Heart of the Nearby Galaxy

The celestial core of Messier 77 is located in such a way that dust and gas circulating around the black hole obscure the object when viewed from Earth using typical methods such as telescopes that rely on optical light.

“We’re looking at the galaxy a little bit from the side, and because we’re looking at it from the side, the black hole is hiding behind material orbiting close to it,” said Ignacio Taboada, a professor of physics at the Georgia Institute of Technology. andsman for the international collaboration that carried out the research.

But neutrinos, the most abundant energetic particles in the universe,pass through such gas and dust without being affected because they rarely interact with anything, including magnetic fields, matter, or gravity. This ghostly appearance offers scientists an unprecedented means to investigate the processes going on around the previously hidden black hole, including how it accelerates superhot, charged gas and matter in the vicinity, the researchers said.

“Neutrinos are a different way of looking at the universe. And every time you look at the universe in a new way, you learn something that you could not have learned with the old methods,” said Dr. Taboada.

Neutrinos retain information. that was imprinted when they were generated at their sources, including their energies, according to Hans Niederhausen, a postdoctoral associate at Michigan State University who was involved in the research. That same energy is brought to Earth along with neutrinos.

Now that they know where certain neutrinos come from, the researchers are studying them to better understand where the interactions occur within Messier 77 that create and accelerate these particles, and the behavior and nature of the black hole itself, Dr. Niederhausen said. .

They also plan to comb the cosmos for other neutrinos from galaxies with active supermassive black holes similar to Messier 77. This galaxy “gives us a very good idea of ​​where to look next,” he added.

The neutrino detector telescope used in the study, known as the IceCube Neutrino Observatory, is buried in a billion tons of ice around the US Amundsen-Scott South Pole Station. As neutrinos pass through the Earth, they occasionally collide with atoms in the ice. The observatory’s more than 5,000 basketball-sized sensors detect the byproducts of those rare collisions and send that data to computers on the surface.

The $279 million observatory, funded primarily by the National Science Foundation, was completed in 2011 and detects about 100,000 neutrinos a year. Almost all of those neutrinos are created by processes in our atmosphere, but a few hundred neutrinos detected annually originate outside our solar system, known as astrophysical neutrinos.

Because neutrinos penetrate matter and they pass unaffected, traveling unerringly in a straight line from their point of creation. So, by plotting an astrophysical neutrino’s direction of travel through the ice, researchers can piece together its path back through the universe to its origin.

Nearly 400 scientists from more than 50 institutions make up the international IceCube collaboration, which analyzed data collected by the observatory between 2011 and 2020 to identify 79 neutrinos that originated from Messier 77.

That IceCube is finding individual objects that are sources of astrophysical neutrinos is “absolutely amazing,” said Dr. Yoshi Uchida, a professor of physics at Imperial College London who was not involved in the study. “After operating for 10 years, it is turning neutrino observation into another source of information.”

Dr. Taboada said that he believes IceCube will continue to receive more neutrinos from this galaxy. Those future detections could not only help analyze additional details about Messier 77’s supermassive black hole, but could also help answer the “oldest question in astronomy,” according to Francis Halzen, a physicist at the University of Wisconsin-Madison and a researcher. IceCube main.

Scientists have known about cosmic rays, streams of high-energy protons, and atomic nuclei that travel at near-light speeds and create electromagnetic radiation and showers of subatomic particles when they strike Earth’s atmosphere for more than a century. But the origin of these rays, and what mechanism speeds them up and sends them in our direction, remains a mystery.

“Something in the universe gave them a huge kick to make them go so fast,” Dr. Niederhausen said of cosmic rays.

Neutrinos are a byproduct of those cosmic rays’ interactions with the matter and radiation surrounding high-energy objects like supermassive black holes, so Drs. Halzen and Taboada said that tracing the ghostly particles back to their origins could also help resolve the origins of cosmic rays.

Write Aylin Woodward at aylin.woodward@wsj.com